A magnetic disk device generates a write current based on a data pattern of write data, and writes the data on a disk based on the generated write current. When generating the write current, the magnetic disk device may not be able to detect a portion of the data pattern of the write data. In this case, the magnetic disk device generates a write current based on the data pattern of the write data of which a portion is lost. Thus, a data error may occur in the data written based on the write current. The magnetic disk device may detect the data in which the data error occurs, by reading the written data and executing write verification thereon. However, when the write verification is executed each time data is written on the disk, the write performance of the magnetic disk device will be deteriorated.